Disklike storage medium and tracking method using the same

ABSTRACT

A disklike storage medium on which information is recorded at higher density by reducing the redundancy of the address part and a tracking method using the medium are disclosed. The disklike storage medium where a track is divided into areas and address data is recorded in the areas is so adapted that an error detecting code for identifying the data common to adjacent tracks out of the address data is added to the common data. Thus, a data synchronization processing performed when the address data is reproduced is realized without any special synchronization pattern.

TECHNICAL FIELD

The present invention relates to a disk-shaped storage medium on or fromwhich data is recorded or reproduced using a laser beam, and to atracking method using the disk-shaped storage medium.

BACKGROUND ART

Recently, as disk-shaped storage media, optical disks have been put intopractical use as large capacity data files and media for storing musicor images. However, it further is intended to increase the capacities ofsuch disk-shaped storage media so that they can be applied in morevarious uses. For efficient access to a large capacity optical disk, thefollowing method is employed in general. That is, recording data aredistributed to sectors in a certain unit of data size, and recording andreproduction are performed using the sectors as base units forrewriting. To the respective sectors as the base units for rewriting,addresses for identifying the sectors are added. Generally, theaddresses are recorded as pits formed of concave and convex parts in anoptical disk. A land/groove recording system has been employed commonly.In the system, track-guide grooves and inter-groove portions are used asareas for recording data in order to increase the density in a trackdirection.

A conventional optical disk having this sector configuration isdescribed with reference to FIG. 12.

In FIG. 12(a), numeral 1001 indicates a substrate, numeral 1002 arecording film, numeral 1003 a first track, numeral 1004 a second track,numeral 1005 a sector of a divided portion of the track, numeral 1006 anaddress for identifying the sector, and numeral 1007 a data recordingarea for recording data. The first track 1003 is formed of a groove andthe second track 1004 is formed of an inter-groove portion sandwiched bythe groove of the first track. As shown in FIG. 12(a), the first track1003 and the second track 1004 are configured to be positionedalternately on a one-revolution basis. Tracking by an optical beam isperformed using the groove as a guide. However, the first track 1003 isin the groove and the second track 1004 is on the inter-groove portion,and therefore a tracking polarity is required to be inverted for theshift between the first track and the second track. As marks serving fordetecting the polarity inversion, polarity inversion marks 1008 areprovided in locations where the shift between the first track and thesecond track takes place. An optical disk device inverts the polarity intracking using the polarity inversion marks 1008. In the sector 1005,the address 1006 and the data recording area 1007 are arranged as shownin FIG. 12(b).

Furthermore, as shown in FIG. 12(c), the address 1006 added foridentifying the sector 1005 includes a sector mark 1009 indicating asector starting point, a VFO mark 1010 used for generating a clock forthe reproduction of the address part, an address mark 1011 forindicating the start of address data, a sector number 1012, a tracknumber 1013, and an error detection code 1014. Since the sector mark1009 and the address mark 1011 provide a data pattern for identifyingthe start of the address data, the data pattern is required to be aunique pattern that does not appear in the sector number 1012, the tracknumber 1013, and the error detection code 1014. Therefore, the addressdata of the sector number 1012, the track number 1013, and the errordetection code 1014 are recorded after being processed by bi-phasemodulation or run-length-limiting modulation (RLL modulation). By thismodulation process, a data pattern that does not appear from modulationrules for the other data can be obtained. Thus, a unique data patternnot in accordance with the modulation rules is used for the sector mark1009 and the address mark 1011. The sector mark 1009 has a sufficientlength to identify the start of the address area easily even when a PLLclock for synchronization is not locked.

As the modulation to the address data portion, the conventional exampleshown in FIG. 12 employs a bi-phase modulation in which “0” is modulatedto be “00” or “11”, and “1” to be “10” or “01”. According to thismodulation, a pattern with at least three “1” or “0” in a row is changedinto a unique pattern not in accordance with the modulation rules. Asthe pattern not in accordance with the modulation rules, theconventional example shown in FIG. 12 employs “10001110” for the addressmark 1011 and “111111110000000” for the sector mark 1009. A method ofreproducing the address part in this conventional example is describedbriefly as follows.

Initially, the sector mark is detected. The sector mark has a uniquepattern having eight “1” and eight “0” consecutively. When a mark withat least a certain length is detected using a free-running PLL clock,the sector mark 1009 can be detected easily. When this sector mark 1009is detected, the PLL clock used for address demodulation is locked bythe subsequent VFO 1010. After the lock of the PLL clock, the PLL clockdetermines “1” and “0” of the reproduced data, thus obtainingdetermination data. When the pattern of“10001110” as the address mark1011 is detected from the determination data, the subsequent data areidentified as the sector number 1012, the track number 1013, and theerror detection code 1014. In this way, the detection of the addressmark 1011 allows the subsequent data to be identified as the sectornumber 1012, the track number 1013, and the error detection code 1014that are to be demodulated. Thus, the data are demodulated.

In the above-mentioned conventional example, the address part 1006includes the VFO mark 1010 for clock synchronization. However, a methodin which the clock for demodulating address data is obtained by anothermeans also has been practiced. This type of conventional example isdescribed with reference to FIG. 13.

In FIG. 13(a), numeral 1101 indicates a substrate, numeral 1102 arecording film, numeral 1103 a track, numeral 1104 a sector of a dividedportion of the track, numeral 1105 a segment of a divided portion of thesector, numeral 1106 an address for identifying the sector, and numeral1107 a data recording area for recording data.

As shown in FIG. 13(b), in the leading location of the segment 1105,wobble pits 1108 used for obtaining a tracking signal and the subsequentclock pit 1109 for generating a clock for address and data demodulationare provided. As shown in FIG. 13(c), the address 1106 added to identifythe sector 1104 includes an address mark 1110 for indicating the startof the address data, a sector number 1111, a track number 1112, and anerror detection code 1113. As in the above-mentioned conventionalexample, the address mark 1110 has a unique pattern that does not appearin the sector number 1111, the track number 1112, and the errordetection code 1113. Similarly in the conventional example shown in FIG.13, the bi-phase modulation is employed for modulating the address dataportion and “10001110” is used as the address mark 1110 as in theabove-mentioned conventional example.

A method of reproducing the address part in this conventional example isdescribed briefly as follows. Initially, the clock pit 1109 is detected.Using this clock pit, the frequency of a clock pit detection signal ismultiplied by N using the PLL, thus generating a PLL clock for addressdemodulation. In the trailing part of the PLL clock, as in theabove-mentioned conventional example, “1” and “0” of the reproduced dataare determined, thus obtaining determination data. When the pattern of“10001110” as the address mark 1110 is detected from this determinationdata, the subsequent data are identified as the sector number 1111, thetrack number 1112, and the error detection code 1113. In this way, thedetection of the address mark 1110 allows the subsequent data to beidentified as the sector number 1111, the track number 1112, and theerror detection code 1113 that are to be demodulated. Thus, the data aredemodulated.

In a conventional optical disk, however, a unique pattern that does notappear in an address data portion has been required as an address markto identify the starting position of an address. Therefore, recordingwas performed after the process of the data portion of the address bythe bi-phase or RLL modulation. In a 1-7 modulation or 2-7 modulation asa type of bi-phase modulation or RLL modulation, one bit of address databecomes two bits or 1.5 bits after the modulation, thus increasingredundancy. Therefore, there has been a problem that the area requiredfor the address data portion increases and thus the data recording areais reduced.

Moreover, in a conventional magneto-optical disk, in order to reproducethe first track and the second track continuously, a detection pit fortracking polarity inversion is provided, which also has been a factorthat reduces the area in or from which data are recorded or reproduced.Furthermore, in the case of using one bit of the polarity inversiondetection pit, it has been difficult to secure sufficient reliabilitywith respect to defects of the disk and damages on the disk surface.

DISCLOSURE OF THE INVENTION

The present invention is intended to solve the aforementioned problemsand to provide an optical disk in which the redundancy of an addresspart is reduced to enable high density information recording, and atracking method using such an optical disk.

In order to achieve the above-mentioned object, a first disk-shapedstorage medium according to the present invention includes a trackdivided into a plurality of areas and in the plurality of areas, addressdata are positioned. Error detection codes are added to data common toadjacent tracks of the address data for identifying the data common toadjacent tracks. According to this configuration, an effect can beobtained in that a synchronous process can be performed on data inaddress data reproduction without using a unique synchronizationpattern.

In the first disk-shaped storage medium, it is preferable that the datacommon to adjacent tracks are positioned at a track pitch allowing thedata common to adjacent tracks to be reproduced either on the track orin locations sandwiched by the track. This enables information usefulfor control to be read out from the optical disk without trackingcontrol.

In order to achieve the above-mentioned object, a second disk-shapedstorage medium according to the present invention has two tracks havingdifferent tracking polarities and being positioned alternately on aone-revolution basis. The tracks are divided into a plurality of areasand address data are positioned in the plurality of areas. Errordetection codes are added to data common to adjacent tracks of theaddress data for identifying the data common to adjacent tracks. Thedata common to adjacent tracks include circumferential positioninformation and are positioned at a track pitch allowing the data commonto adjacent tracks to be reproduced either on the tracks or in locationssandwiched by the track. According to this configuration, the datacommon to adjacent tracks and the error detection codes for identifyingthe data common to adjacent tracks are read out without trackingcontrol. Based on them, the switching of the tracking polarities can bedetected.

In the first and second disk-shaped storage media, it is preferable thatthe address data are distributed to be positioned in the plurality ofareas as one bit each. According to this, it is not necessary toaccelerate a shift register storing the data common to adjacent tracksand the error detection codes identifying the data common to adjacenttracks in order to identify them in address data reproduction. Thus, thesynchronous process to data can be performed easily.

In the second disk-shaped storage medium, it is preferable that the twotracks having different tracking polarities and being positionedalternately on a one-revolution are formed of tracks subjected to thetracking control by pairs of wobble marks positioned in locations in theplurality of areas into which the tracks are divided. The locations areshifted to the left and right with respect to the centers of the tracksand are spaced at a certain distance in a track-running direction.Respective positions of the wobble marks as a pair are changedalternately on the one-revolution basis. According to this, the trackingcontrol is performed while the positions of the wobble marks, i.e. thepolarities of tracking error signals are switched every revolution.Consequently, the track pitch can be reduced to increase the density ofthe tracks, while the one-spiral track configuration advantageous incontinuously recording and reproducing mass data is maintained.

In order to achieve the above-mentioned object, a tracking methodaccording to the present invention is characterized by the following. Adisk-shaped storage medium is used. In the disk-shaped storage medium,two tracks with different tracking polarities are divided into aplurality of areas. Address data are positioned in parts of theplurality of areas. Error codes are added to data common to adjacenttracks of the address data for identifying the common data. The commondata include circumferential position information and are positioned ata track pitch allowing the common data to be reproduced both on thetracks and between the tracks. Using this disk-shaped storage medium,starting points of the address data are detected based on the commondata and the error detection codes. From the starting points, thecircumferential position information is detected and the trackingpolarities are determined from the position information. Thus, trackingcontrol is performed. This method enables the switching of the trackingpolarities to be detected easily.

In the first disk-shaped storage medium, it is preferable that pitsproducing the timings for demodulation of the address are positioned ata track pitch allowing the pits to be reproduced either on the track orin locations sandwiched by the track.

In order to achieve the above-mentioned object, an address reproductionmethod according to the present invention is characterized by thefollowing. A disk-shaped storage medium is used. In the storage medium,a track formed of a groove and an inter-groove portion or of aninter-groove portion alone is divided into a plurality of areas. In theplurality of areas, address data are positioned. Using this storagemedium, reference positions for producing the timings for demodulationof the address data are produced from the starting ends or the trailingends of the grooves of the track divided into the plurality of areas.

In the first disk-shaped storage medium, it is preferable that the trackis formed of a groove or an inter-groove portion and is divided into aplurality of areas and the address data are distributed to be positionedin the plurality of areas as one bit each at the positions of startingends or trailing ends of the grooves divided into the plurality ofareas.

In the first disk-shaped storage medium, it is preferable that the trackis formed of a groove or an inter-groove portion and is divided into aplurality of areas and the address data are distributed to be positionedin the plurality of areas as one bit each at the positions of thestarting ends of the grooves divided into the plurality of areas and thetrailing ends of the grooves divided into the plurality of areas arealigned to be arranged at radially corresponding positions.

According to the above-mentioned configuration and methods, in order toidentify the starting position of the address, it is not required tomodulate the address data portion and to use a unique pattern obtainedby the modulation rules as address marks. Therefore, the redundancy ofthe address part can be reduced considerably, thus achieving ahigh-density optical disk.

In the optical disk of the present invention, the positions where thetracking polarities are switched can be detected before a trackingpull-in operation. Therefore, in an optical disk with a track pitchproviding a high-density track, a stable tracking pull-in operation canbe performed.

Furthermore, the tracking control performed according to the signalsfrom the wobble pits while recording and reproduction are performed onlyin groove portions enables the track pitch to be reduced and thedifference in the recording/reproduction characteristics between tracksto be eliminated simultaneously.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1(a), 1(b), and 1(c) are a general structural drawing, a drawingof a segment structure, and a drawing illustrating an address area,respectively, of an optical disk according to a first embodiment of thepresent invention.

FIG. 2 is a block diagram of an address demodulator in the case of usingthe optical disk according to the first embodiment of the presentinvention.

FIG. 3 is a diagram illustrating an operation of address demodulation inthe case of using the optical disk according to the first embodiment ofthe present invention.

FIG. 4 is a diagram illustrating a synchronous process in addressdemodulation in the case of using the optical disk according to thefirst embodiment of the present invention.

FIGS. 5(a), 5(b), and 5(c) are a general structural drawing, a drawingof a segment structure, and a drawing illustrating an address area,respectively, of an optical disk according to a second embodiment of thepresent invention.

FIG. 6 is a drawing illustrating a tracking configuration of the opticaldisk according to the second embodiment of the present invention.

FIG. 7 is a block diagram of a tracking-polarity detector in the case ofusing the optical disk according to the second embodiment of the presentinvention.

FIGS. 8(a) and 8(b) are a general structural drawing and a drawing of asegment structure, respectively, of an optical disk according to a thirdembodiment of the present invention.

FIGS. 9(a), 9(b), and 9(c) are drawings illustrating data positions inan address part of the optical disk according to the third embodiment ofthe present invention.

FIGS. 10(a) and 10(b) are a general structural drawing and a drawing ofa segment structure, respectively, of an optical disk according to afourth embodiment of the present invention.

FIGS. 11(a) and 11(b) are a general structural drawing and a drawing ofa segment structure, respectively, of an optical disk according to afifth embodiment of the present invention.

FIGS. 12(a), 12(b), and 12(c) are a general structural drawing, adrawing of a segment structure, and a drawing illustrating an addressarea, respectively, of a conventional optical disk.

FIGS. 13(a), 13(b), and 13(c) are a general structural drawing, adrawing of a segment structure, and a drawing illustrating an addressarea, respectively, of another conventional optical disk.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are described with reference to thedrawings as follows.

First Embodiment

FIGS. 1(a), 1(b), and 1(c) show a general structural drawing, a drawingof a segment structure, and a drawing illustrating an address area,respectively, of an optical disk according to a first embodiment of thepresent invention.

In FIG. 1(a), numeral 101 indicates a substrate, numeral 102 a recordingfilm, numeral 103 a track, numeral 104 a sector of a divided portion ofthe track, numeral 105 a segment of a divided portion of the sector,numeral 106 an address for identifying the sector, and numeral 107 adata recording area for recording data. The track 103 is divided into 32sectors 104 around the disk. Further, the sector 104 is divided into 40segments 105, and the address 106 is recorded in the first segment.

As shown in FIG. 1(b), in the leading location of the segment 105, aclock pit 108 for generating a clock and wobble pits 109 and 110 usedfor obtaining a tracking signal are provided. A tracking system in thepresent embodiment is a sample servo system in which tracking isperformed by allowing quantities of reflected lights from the wobblepits 109 and 110 to be equal.

As shown in FIG. 1(c), the address 106 added to identify the sector 104includes an 8-bit sector number 111, an error detection code 112 foridentifying the sector number, a 16-bit track number 113, and anaddress-data error detection code 114. It is one of the importantcharacteristics of the present invention to employ an address format inwhich the error detection code 112 for identifying a data common toadjacent tracks is added to the data (the sector number 111 in thepresent embodiment) common to adjacent tracks. By using this errordetection code 112, the synchronous process to the address data can becarried out. In the present embodiment, an 8-bit CRC error detectioncode is used as the error detection code 112 for the sector number and a14-bit CRC error detection code as the error detection code 114 for theaddress number. With respect to the address data 111, 112, 113, and 114,no modulation such as bi-phase modulation or the like, which has beencarried out conventionally, is performed, and the address data arerecorded as a bit string of “1” and “0”.

The data bits required when such address data are recorded by theconventional system in which data are recorded after being subjected tobi-phase modulation are 8 bits (an address mark)+16 bits (the sectornumber after the bi-phase modulation)+32 bits (the track number afterthe bi-phase modulation)+28 bits (the address-data error detection codeafter the bi-phase modulation)=84 bits. On the other hand, in theoptical disk of the present invention, the address data are recordedwithout a modulation process such as the bi-phase modulation. Therefore,the bits required for the address part can be reduced considerablycompared to that in the conventional system and are 8 bits (the sectornumber)+8 bits (the sector-number error detection code)+16 bits (thetrack number)+14 bits (the address-data error detection code)=46 bits.When the address is demodulated in such an optical disk, the synchronousprocess to demodulation data substituted for the conventional addressmark is required. This method is described as follows.

FIG. 2 is a block diagram of an address demodulator for demodulating theaddress 106 using the optical disk according to the present embodiment.FIG. 3 is a timing chart of the address demodulator. A method ofreproducing the address 106 in the optical disk according to the presentembodiment is described with reference to FIGS. 2 and 3.

In FIG. 2, numeral 201 indicates a clock pit detector, numeral 202 a PLLfor generating a clock for address demodulation from a clock pit,numeral 203 a determinator for determining “1” and “0” of the addressdata in the trailing section of the PLL clock, numeral 204 a 16-bitshift register capable of storing an 8-bit sector number 111 and an8-bit sector-number error detection code 112, numeral 205 a CRC errordetector for detecting an error in contents of the shift register 204,numeral 206 a timing generator for generating demodulation timings forthe track number 113 and the address-data error detection code 114,numeral 207 a shift register preserving the track number, and numeral208 a CRC error detector for detecting an error in the address data.

Initially, it is necessary to generate a reference clock fordemodulating the address. The reference clock is generated based on theclock pit 108. In the present embodiment, as indicated with numeral 301in FIG. 3, there are 200 address data bits between the clock pit 108 atthe leading end of the segment 105 and the clock pit 108 at the leadingend of the subsequent segment. When based on a clock pit signal 302detected by the clock pit detector 201, a clock with a frequency 200times higher than that of the clock pit signal 302 is generated by thePLL 202, a clock 303 synchronized with the address data bits can beobtained. At the trailing end of the PLL clock 303, “1” and “0” aredetermined by the determinator 203, thus obtaining demodulation data304. This demodulation data 304 is read by the shift register 204 and anerror in contents of the shift register 204 is determined by the errordetector 205.

FIG. 4 shows an operation of the shift register 204 and the errordetector 205. As shown in FIG. 4, the CRC error of the sector numberdoes not occur only when the whole sector number 111 and sector-numbererror detection code 112 are loaded on the shift register 204. In thiscase, an output 305 from the error detector 205 is 0. In other words, bydetecting errors in the sector number 111 and the error detection code112 accompanying the sector number, the position where no error occursis determined uniquely. Therefore, the address data can be synchronizedwithout using an address mark code. From the output 305 of the errordetector 205, timing signals 306 and 307 (see FIG. 3) for operating theshift register 207 for the track number and the address-data errordetector 208 can be generated by the timing generator 206. When theshift register 207 storing the track number and the error detector 208are operated based on the timing signals 306 and 307, the address can bedemodulated.

As described above, by the addition of an error detection code to a datacommon to adjacent tracks, the address part can be demodulated withoutmodulating the address data. Thus, the redundancy of the address partcan be reduced considerably.

Second Embodiment

FIGS. 5(a), 5(b), and 5(c) show a general structure, a segmentstructure, and an address area, respectively, of an optical diskaccording to a second embodiment of the present invention.

In FIG. 5(a), numeral 501 denotes a substrate, numeral 502 a recordingfilm, numeral 503 a first track, numeral 504 a second track, numeral 505a sector of a divided portion of the track, numeral 506 a segment of adivided portion of the sector, numeral 507 an address for identifyingthe sector, and numeral 508 a data recording area for recording data.The first track 503 and the second track 504 are divided into 32 sectors505 around the disk. The sector 505 further is divided into 40 segments506. The address 507 is recorded in the first segment. The other secondto fortieth segments serve as the data recording area 508.

As shown in FIG. 5(b), in the leading location of the segment 506, aclock pit 509 for generating a clock and a pair of wobble pits 510 and511 used for obtaining a tracking signal are provided. The trackingsystem in the present embodiment also is a sample servo system as in thefirst embodiment. In the present embodiment, in order to increase thedensity in a track direction, the first track 503 and the second track504 having different tracking polarities in the sample servo system arepositioned alternately on a one-revolution basis.

FIG. 6 shows the position relationship of the wobble pits 510 and 511 tothe first track 503 and the second track 504. As shown in FIG. 6, thefirst track 503 and the second track 504 are configured spirally andcontinuously while being positioned alternately on a one-revolutionbasis in the disk (hereinafter, referred to as “a single-spiral polarityswitching type sample servo system”). However, between the first track503 and the second track 504, the positions of the wobble pits 510 and511 are different and therefore the tracking polarity is inverted. Thus,two positive and negative polarity positions of the tracking signals areused, thus achieving a track pitch allowing the track density to bedoubled. For the continuous recording and reproduction with respect toan optical disk with such a track configuration, it is necessary toinvert the tracking polarity every revolution of the disk.

In the conventional optical disk, as shown in FIG. 12, a detection pit(a polarity inversion mark) 1008 for polarity inversion is provided inthe part where a track with one polarity shifts to that with the otherpolarity, and using this pit as a reference, the tracking polarity isswitched. In the present embodiment, without using thispolarity-inversion detection pit, the tracking polarities of the firsttrack 503 and the second track 504 can be switched.

As shown in FIG. 5(c), the address 507 in the present embodimentincludes an 8-bit sector number 512, a sector-number error detectioncode 513, a track number 514 for the first track 503, an address-dataerror detection code 515 for the first track 503, a track number 516 forthe second track 504, and an address-data error detection code 517 forthe second track 504. As in the first embodiment, the error detectioncode 513 is added to a data (the sector number 512 in the presentembodiment) common to adjacent tracks, and the pits of the address 507are arranged as shown in FIG. 5, which are important characteristics ofthe present invention.

As shown in FIG. 5, data 512 and 513 common to tracks adjacent in aradial direction of the disk are recorded at the same positions in thefirst track 503 and the second track 504 and data 514 and 515 and data516 and 517 are not common to adjacent tracks and are arranged atdifferent positions. According to this positioning, the sector number512 and the error detection code 513 are positioned with a high densityin the radial direction of the disk and also are the data common toadjacent tracks. Therefore, reproduction can be performed withouttracking control. In this case, the pitch of tracks adjacent in theradial direction of the disk is set so that, for example, the intervalbetween the center of an address pit and that of the address pitadjacent thereto is around half the breadth of a beam spot or less. Theuse of such characteristics enables the process of inverting a trackingpolarity at the boundary between the first track 503 and the secondtrack 504. This method is described with reference to FIG. 7.

FIG. 7 is a block diagram of a tracking polarity detector in the presentembodiment. In FIG. 7, numeral 701 is a clock pit detector, numeral 702a PLL for generating a clock for address demodulation based on the clockpit 509, numeral 703 a determinator for determining “1” and “0” of theaddress data in the trailing end of the PLL clock, numeral 704 a 16-bitshift register capable of storing the 8-bit sector number 512 and the8-bit sector-number error detection code 513, and numeral 705 a CRCerror detector for detecting an error in contents of the shift register704, which are configured as in the first embodiment. In order to invertthe tracking polarity, besides the above-mentioned configuration, thepresent embodiment further includes a polarity-switching-sectordeterminator 706 for detecting, from the sector number read out, thesector in which the polarity switches over and a tracking-polarityinverter 707.

As described above, the sector number 512 and the sector-number errordetection code 513 accompanying the sector number can be reproduced in atracking-off state. As in the first embodiment, it can be confirmed bythe error detector 705 that the sector number has been read outcorrectly. It is determined by the polarity-switching-sectordeterminator 706 that the sector number read out correctly indicates thesector in which the tracking polarity is switched, thus switching(inverting) the tracking polarity by the tracking polarity inverter 707.As described above, according to the optical disk of the presentembodiment, the position where the tracking polarity switches over canbe detected before the tracking operation.

In a system of switching the tracking polarities by detecting apolarity-switching pit in a conventional optical disk, thetracking-polarity switching position is detected only when the trackingoperation is performed. Therefore, there has been a problem that thetracking in the vicinity of the tracking-polarity switching positioncannot be pulled in stably. In the optical disk according to the presentembodiment, however, as described above, the tracking-polarity switchingposition is detected before the tracking pull-in operation, thusachieving constantly a stable tracking pull-in operation. The address507 in the present embodiment can be demodulated by the same method asin the first embodiment.

In the present embodiment, the above description was directed to theconfiguration in which the sector number determined by the errordetector 705 as being read out correctly is determined by thepolarity-switching-sector determinator 706 as being the sector in whichthe tracking polarity switches over, and the tracking polarities areswitched (inverted) by the tracking polarity inverter 707. In additionto such a configuration, for instance, it also is possible to configurethe optical disk so that the length and number of clock marks are variedevery revolution to detect the tracking-polarity switching position bydetecting the characteristics of the clock marks. This enables thepolarity to be confirmed in all the segments, thus allowing thetracking-polarity switching positions to be detected more stably at ahigher speed.

Third Embodiment

FIG. 8(a) and FIG. 8(b) show a general structure and a segmentstructure, respectively, of an optical disk according to a thirdembodiment of the present invention.

In FIG. 8(a), numeral 801 indicates a substrate, numeral 802 a recordingfilm, numeral 803 a first track, numeral 804 a second track, and numeral805 a segment obtained by dividing the tracks into 1280 segments. Asshown in FIG. 8(b), in the leading location of the segment 805, a clockpit 806 for generating a clock, a pair of wobble pits 807 and 808 usedfor obtaining a tracking signal, and an address pit 809 arranged so thatthe address data are distributed to be positioned as one bit each. Thetracking system in the present embodiment is the single-spiral polarityswitching type sample servo system as in the second embodiment.

In the present embodiment, the address data is decomposed into one-bitdata to be arranged in the segments 805, which is an importantcharacteristic. In the first and second embodiments, the CRC errordetector 205 or 705 is required to perform the shifting operation for 16times during a one-bit shift of the shift register 204 or 704.Therefore, a high-speed clock is required, and it has been difficult toincrease the address transfer rate. In the present embodiment, however,when the address pits 809 are distributed and arranged in the segments805, time margin is obtained between reproduction of one bit of anaddress pit 809 and the reproduction of the subsequent address pit 809.During the time margin, the error detector can operate and therefore thesystem can be operated at a high speed. In addition, all the segments805 have the same physical structure, and therefore the flexibility ofthe format can be improved considerably.

The configuration of the address data according to the presentembodiment is described in detail with reference to FIG. 9. In FIG. 9,numeral 811 indicates a segment number, numeral 812 an error detectioncode for detecting an error in the segment number 811, numeral 813 atrack number of the first track 803, numeral 814 an error detection codefor the track number 813, numeral 815 a track number of the second track804, and numeral 816 an error detection code for the track number 815.

As shown in FIG. 9, a set of address data is produced by gathering theaddress pits 809 in 80 segments. Since one track has 1280 segments, 16sets of address data can be produced per track. In the first and secondembodiments, an error detection code was added to a sector number asdata common to adjacent tracks. In the present embodiment, onecorresponding to the sector number is the segment number 811. As shownin FIG. 9, the segment number 811 as data common to adjacent tracks andthe error detection code 812 for the segment number 811 are recorded inboth the first track 803 and the second track 804 and can be read outwithout tracking control. Thus, as in the second embodiment, the segmentnumber can be detected in a tracking-off state and the process ofinverting the tracking polarity also can be achieved.

As shown in FIG. 9, the track number 813 and the error detection code814 for the track number 813 in the first track 803 and the track number815 and the error detection code 816 for the track number 815 in thesecond track 804 are arranged so that the address pits 808 are notpresent in both adjacent tracks. This is intended to reduce errors dueto crosstalk between adjacent tracks in reading out the address.Similarly in the present embodiment, when the address pits 809 in thesegments 805 are gathered, the same format as in the first embodiment isobtained. Therefore, the address can be synchronized and demodulated bythe same method as in the first embodiment, thus obtaining the sameeffects as in the first embodiment.

Fourth Embodiment

FIGS. 10(a) and 10(b) show a general structure and a segment structure,respectively, of an optical disk according to a fourth embodiment of thepresent invention. The fourth embodiment is different from the thirdembodiment with respect to the clock pit 806 and the tracking system.

In FIG. 10, numeral 1001 indicates a substrate, numeral 1002 a recordingfilm, numeral 1003 a first track, numeral 1004 a second track, andnumeral 1005 a segment obtained by dividing tracks into 1280 segments.The first track 1003 is formed of inter-groove portions separated,segment 1005 by segment 1005. The second track 1004 is formed of groovesseparated, segment 1005 by segment 1005. These two tracks are arrangedalternately on a one-revolution basis with a land/groove single spiralstructure.

FIG. 10(b) shows an enlarged view of the segments 1005. The area forrecording data includes grooves 1006 and inter-groove portions betweenthe grooves 1006. The grooves 1006 are separated, segment 1005 bysegment 1005. Address pits 1007 are positioned in the separated groovesand inter-groove portions. Leading end positions 1008 or trailing endpositions 1009 of the grooves 1006 of the data recording area arealigned radially and serve as clock position information. This has thesame function as that of the clock pit in the third embodiment.

In the present embodiment, the trailing ends 1009 are used as clockposition information. However, the leading ends 1008 also may be used asthe clock position information.

The tracking system in the present embodiment is a single-spiralpolarity switching type groove tracking system using the intensity ofdiffracted light and reflected light from the grooves 1006. Similarly inthis system, the address pits 1007 can be demodulated by the PLL clockextracted from the clock position information 1009. Therefore, in thetracking polarity switching system and the address demodulation system,the same effects as in the second and third embodiments can be obtained.Furthermore, the address format obtained by gathering the address bitdata 1007 is equivalent to that in the third embodiment, and the effectsequivalent to those in the third embodiment can be obtained.

Fifth Embodiment

FIGS. 11(a) and 11(b) show a general structure and a segment structure,respectively, of an optical disk according to a fifth embodiment of thepresent invention. The fifth embodiment is different from the thirdembodiment with respect to the forms of the clock pits 806 and theaddress pits 809.

In FIG. 11, numeral 1101 indicates a substrate, numeral 1102 a recordingfilm, numeral 1103 a first track, numeral 1104 a second track, andnumeral 1105 a segment obtained by dividing the tracks into 1280segments. As shown in FIG. 11(b), in the segments 1105, grooves 1106 asareas for recording data and pairs of wobble pits 1107 and 1108 used forobtaining tracking signals are positioned. The leading end positions1109 of the grooves 1106 as the data recording areas are shiftedcorresponding to address data “1” and “0”. According to this, theaddress data are distributed to be positioned in the segments 1105 asone bit each. The leading end positions 1109 of the grooves 1106 have afunction equivalent to that of the address pits in the third embodiment.In addition, trailing end positions 1110 of the grooves 1106 are alignedand serve as clock position information. This has the same function asthat of the clock pits in the third embodiment.

In the present embodiment, the leading ends 1109 were used as addressbit data and the trailing ends 1110 as the clock position information.Conversely, however, the leading ends 1109 may be used as the clockposition information and the trailing ends 1110 as the address bit data.

However, the present embodiment provides a shorter interval between theclock detection reference positions 1110 of the trailing ends of thegrooves 1106 and the leading end positions 1109 of the grooves 1106corresponding to the address bits “1” and “0”. Jitter precision of theclock extracted from the trailing end positions 1110 is degraded withthe distance from the trailing end positions 1110. The addressdemodulated using this clock also is affected by the jitter. Therefore,the nearer the position of the address bit is to the trailing endpositions 1110 as the position reference of the clock, the higher theaddress detection precision becomes, thus decreasing the error rate. Forthe above-mentioned reasons, better effects can be obtained when theleading end positions 1109 are used as the address bit data and thetrailing end positions 1110 as the clock position information.

The tracking system in the present embodiment is the single-spiralpolarity switching type sample servo system as in the second and thirdembodiments. Therefore, in tracking control, the effect equivalent tothat in the second and third embodiments can be obtained.

The address format obtained by gathering the address bit data 1109 isequivalent to that in the third embodiment. Therefore, the effectequivalent to that in the third embodiment can be obtained.

Furthermore, in the present embodiment, the area for recording data isformed of the grooves 1106. Usually, in an optical disk in whichrecording is carried out only in grooves or only in inter-grooveportions through tracking performed using the grooves as a guide, thelimit of the tracking control information obtained from the grooves isabout 1.2 times half the breadth of an optical beam. In order toovercome this limit, a land/groove system is employed, in whichrecording is carried out in both grooves and inter-groove portions.However, the cross-sectional structures of the tracks are different inthe grooves and the inter-groove portions. Therefore, the grooves andthe inter-groove portions have different recording/reproducingcharacteristics, which has been a big problem. This difference in thecharacteristics has been a bigger problem in superresolutionreproduction, requiring a complicated operation of arecording/reproducing film for a reproduction operation, represented bya front aperture system, an in-plane vertical center aperture system, adouble mask system, a domain wall motion system, or the like.

In the present embodiment, however, the tracking control is performedaccording to the signals obtained from the wobble pits 1107 and 1108while recording and reproduction are carried out only in the grooves.Therefore, a track pitch of 1.2 times half the breadth of an opticalbeam or less can be achieved, which was difficult conventionally.

As described above, the present embodiment enables the track pitch to bereduced and the difference in recording/reproducing characteristicsbetween tracks to be eliminated simultaneously.

The embodiments of the present invention were described using sectornumbers and segment numbers as examples of the data common to adjacenttracks. However, the present invention is not limited to this. In anoptical disk, employing a ZCLV or ZCAV system, divided into zones in aradial direction, the common data include zone numbers in the zones,zone constructional information required for the reproduction of thezones, security information for the reproduction of the optical disk,and the like.

Furthermore, the embodiments of the present invention were describedusing an optical disk as an example of a disk-shaped storage medium.However, the present invention also can be applied to, for instance, amagneto-optical data file (MO) and a phase change type disk (PD,DVD-RAM) in which recording and reproduction can be carried out, a ROMdisk used exclusively for reproduction, a recording/reproduction diskfor music (for example, MD), or the like.

What is claimed is:
 1. A disk-shaped storage medium including adjacenttracks divided into a plurality of areas with address data positioned inthe plurality of areas of each track, address data of one track havingdata common to address data of the adjacent track, wherein errordetection codes are added to data common to adjacent tracks foridentifying the data common to adjacent tracks.
 2. The disk-shapedstorage medium according to claim 1, wherein the data common to adjacenttracks are positioned at a track pitch allowing the data common toadjacent tracks to be reproduced either on the tracks or between thetracks.
 3. The disk-shaped storage medium according to claim 1, whereinthe address data are distributed to be positioned in the plurality ofareas as one bit each.
 4. The disk-shaped storage medium according toclaim 1, wherein pits producing timings for demodulation of the addressdata are positioned at a track pitch allowing the pits to be reproducedeither on the tracks or between the tracks.
 5. The disk-shaped storagemedium according to claim 1, wherein the track is formed of a groove oran inter-groove portion and is divided into a plurality of areas, theaddress data are distributed to be positioned in the plurality of areasas one bit each at positions of starting ends of the grooves dividedinto the plurality of areas, and trailing ends of the grooves dividedinto the plurality of areas are aligned to be arranged at radiallycorresponding positions.
 6. The disk-shaped storage medium according toclaim 1, wherein the track is formed of a groove or an inter-grooveportion and is divided into a plurality of areas and the address dataare distributed to be positioned in the plurality of areas as one biteach at positions of starting ends or trailing ends of the groovesdivided into the plurality of areas.
 7. A disk-shaped storage mediumincluding two tracks having different tracking polarities, beingpositioned alternately on a one-revolution basis, and being divided intoa plurality of areas with address data positioned in the plurality ofareas of each track, address data of one track having data common toaddress data of the adjacent track, wherein error detection codes areadded to data common to adjacent tracks including circumferentialposition information of the address data for identifying the data commonto adjacent tracks, and the data common to adjacent tracks arepositioned at a track pitch allowing the data common to adjacent tracksto be reproduced either on the tracks or between the tracks.
 8. Thedisk-shaped storage medium according to claim 7, wherein the addressdata are distributed to be positioned in the plurality of areas as onebit each.
 9. The disk-shaped storage medium according to claim 7,wherein the two tracks having different tracking polarities and beingpositioned alternately on a one-revolution basis are formed of trackssubjected to tracking control by pairs of wobble marks positioned inlocations in the plurality of areas into which the tracks are divided,the locations being shifted to the left and right with respect to acenter of each track and being spaced at a certain distance in atrack-running direction, and respective positions of each pair of wobblemarks are changed alternately on the one-revolution basis.
 10. Atracking method, using a disk-shaped storage medium including twoadjacent tracks with different tracking polarities, the adjacent tracksbeing divided into a plurality of areas with address data positioned inparts of the plurality of areas of each of the adjacent tracks, addressdata of one track having data common to address data of the adjacenttrack, error codes being added to data common to the adjacent tracks foridentifying the data common to adjacent tracks, the data common toadjacent tracks including circumferential position information of theaddress data and being positioned at a track pitch allowing the datacommon to adjacent tracks to be reproduced both on the tracks andbetween the tracks, and comprising: detecting starting points of theaddress data based on the data shared by adjacent tracks and the errordetection codes; detecting the circumferential position information fromthe starting points; determining the tracking polarities from theposition information; and performing tracking control based on thedetermined tracking polarities.